Intervening in the physical development of humans can result in enhancements.

"And now," Mr. Foster went on, "I'd like to show you some very interesting conditioning for the Alpha Plus intellectuals. We have a big batch of them on Rack 5. First Gallery level," he called to two boys who had started to go down to the ground floor.

"They're round about Meter 9000," he explained. "You can't really do any useful intellectual conditioning till the foetuses have lost their tails."